You'd want to find out what local costs are to build, it's typically figured per square foot. Some areas are higher than others. That gives you a ballpark estimate. All the little upgrades add up. A good rule of thumb is whatever your initial estimate is, have at least 20% more ready to deal with various issues and upgrades along the way.

I probably missed a few details, but their numbers on it for a 'class 3' 1800sqft came in around $320k. Stepping down to their 'class 5' came in around $200k. Now, what exactly makes the difference between a $100/sqft house vs $175 is all about the details.